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At least 55 records · Page 3Linked to original sources

PubMed1992

The effect of head-down tilt and water immersion on intracranial pressure in nonhuman primates.

A headward fluid shift occurs in humans exposed to space-flight. This shift is thought to be the stimulus for the observed reduction in plasma volume, and may produce a sustained rise in intracranial pressure (ICP). In order to determine the effect of head-down tilt (HDT) and water immersion on intracranial pressure (ICP), five anesthetized rhesus monkeys were fitted with intracranial pressure-monitoring transducers and subjected to -6 degrees HDT followed by head-out thermoneutral (34.7 degrees) water immersion. ICP was elevated from 3.8 +/- 1.1 mm Hg in the horizontal control period to 5.3 +/- 1.3 mm Hg (p less than 0.05) during the 15 min pre-immersion HDT. When seated in the empty immersion tank, ICP stabilized at -6.3 +/- 1.3 mm Hg for the control period and increased to -2.2 +/- 1.9 mm Hg (p less than 0.05) when the water level was maintained for 30 min at the sternal notch. The ICP returned toward pre-immersion levels (-5.5 +/- 1.4 mm Hg) as the tank was drained. Mean blood pressure (MBP) remained constant during the pre-immersion tilt test. In the pre-immersion control period, MBP was 91 +/- 3 mm Hg compared to 90 +/- 4 mm Hg (p greater than 0.05) during immersion and 82 +/- 1 mm Hg (p less than 0.05) in the post-immersion recovery period. In summary, exposure of rhesus monkeys to either head-down tilt or water immersion produced a prompt rise in ICP during the stimulus period.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerospace Medicine↗

PubMedDate not supplied

[The effect of immersion in distilled water on the engorged larvae and nymphs of Amblyomma cajennense (Fabricius,1787)(Acari: Ixodidae)].

To evaluate the effect of the immersion of engorged larvae and nymphs of Amblyomma cajennense, these stages were immersed by 24, 48, 72 and 96 hours in test tubes containing distilled water. The period of premolt of the nymphs increased proportionally to the time of immersion (p<0.05). The ecdisis period, the longevity and the mortality (days) were similar in all of treatments (p>0.05). The percentage of ecdisis in nymphs was reduced after 72 hours of immersion of the larvae (p<0.05). None of the engorged nymphs survived 96 hours of immersion. The period of the adult premolt increased after 48 hours of immersion (p<0.05). The ecdisis period was similar in the treatments of 24 and 48 hours of immersion (p>0.05). The percentage of ecdisis decreased starting from 24 hours of immersion (p<0.05). There was not statistical difference (p<0.05) between the control group and the 24 hours group of immersion for the parameters longevity and mortality. These findings suggest that the engorged nymphs were more sensitive to the immersion that the engorged larvae.

Animals↗

PubMed1981

Hemodilution, vasopressin suppression, and diuresis during water immersion in man.

We hypothesize that hemodilution in the early stages of water immersion plays an important role in vasopressin (AVP) suppression and subsequent diuresis. Ten men (19-24 years) were immersed to the neck in a semireclining position for 8 h in 34.6 degree C tap water. After 8 h of immersion there were decreases (p less than 0.05) in plasma volume (PV) of 15.6%, extracellular volume (ECV) of 18.8%, interstitial volume (ISV) of 19.6%, and red cell volume of 10.7%. Hemodilution (hyposmotem years) were immersed to the neck in a semireclining position for 8 h in 34.6 degree C tap water. After 8 h of immersion there were decreases (p less than 0.05) in plasma volume (PV) of 15.6%, extracellular volume (ECV) of 18.8%, interstitial volume (ISV) of 19.6%, and red cell volume of 10.7%. Hemodilution (hyposmotem years) were immersed to the neck in a semireclining position for 8 h in 34.6 degree C tap water. After 8 h of immersion there were decreases (p less than 0.05) in plasma volume (PV) of 15.6%, extracellular volume (ECV) of 18.8%, interstitial volume (ISV) of 19.6%, and red cell volume of 10.7%. Hemodilution (hyposmotem of 4 mosmol/kg H2O) and near maximal suppression of AVP (to 0.5 pg/ml) and plasma renin activity (to 0.4 ng Ang 1 .ml-1.h-1) were evident by hour 2 of immersion. The early hemodilution (2-2 h) was due to a slight increase in PV with no change in plasma Na+ or osmotic content, even though urine volume and UosmV increased significantly. The hyposmotemia and PRA suppression continued throughout immersion in spite of the progressively increasing diuresis and decreasing PV. These findings suggest the transfer of hypotonic fluid into the vascular system; this fluid does not appear to come from the intracellular volume. We conclude that hyposmotemia is an important part of the mechanism contributing to AVP suppression during water immersion.

Adult↗

PubMed2002

Shivering endurance and fatigue during cold water immersion in humans.

An important component of survival time during cold exposure is shivering endurance. Nine male and three female healthy and fit subjects [mean (SD) age 24.8 (6.3) years, body mass 71.7 (13.2) kg, height 1.75 (0.10) m, body fat 22.7 (7.4)%] were immersed to the upper chest level in cold water for periods ranging from 105 to 388 min on two occasions to test a prediction of shivering endurance. The water was cooled from 20 to 8 degrees C during the first 15 min of immersion and subsequently rewarmed (<20 degrees C) to elicit a near constant submaximal shivering response. The data were divided according to moderate (M) and high (H) levels of shivering intensity. Respective mean total immersion times were 250 (75) and 199 (80) min ( P=0.086) at different average shivering intensities of 61 (10) and 69 (8)% relative to maximal shivering ( P<0.001). Blood plasma glucose concentration increased during the immersion [from 3.44 (0.54) pre- to 3.94 (0.60) mmol x l(-1) post-immersion ( P=0.037)] and levels were higher during M ( P=0.012). When compared to a model prediction of shivering endurance, shivering activity continued well beyond the predicted endurance times in 18 out of the 24 trials. The average rates of oxygen consumption over the entire immersion period were lower ( P=0.002) during M [0.93 (0.20) l x min(-1)] compared to H [1.05 (0.21) l x min(-1)), and while these rates did not change during the last 90 min of immersion, there was an increase in fat oxidation. There were no trial differences in the average esophageal (T(es)) and mean skin temperatures during the entire immersion period (36.0 and 18.0 degrees C, respectively), yet T(es) decreased ( P=0.003) approximately 0.4 degrees C during the last 90 min of immersion. When the shivering intensity was normalized to account for this decrease, a significant downward trend of approximately 17% x h(-1) in the normalized shivering intensity was found after the predicted end of shivering endurance. These results suggest that shivering drive, and not shivering intensity per se, decreased during the latter stages of the immersion. Underlying mechanisms such as fatigue and habituation for this diminishing cold sensitivity are discussed.

Adaptation, Physiological↗

PubMed2000

Forearm vascular and neuroendocrine responses to graded water immersion in humans.

The hypothesis that graded expansion of central blood volume by water immersion to the xiphoid process and neck would elicit a graded decrease in forearm vascular resistance was tested. Central venous pressure increased (P < 0.05) by 4.2 +/- 0.4 mmHg (mean +/- SEM) during xiphoid immersion and by 10.4 +/- 0.5 mmHg during neck immersion. Plasma noradrenaline was gradually suppressed (P < 0.05) by 62 +/- 8 and 104 +/- 11 pg mL-1 during xiphoid and neck immersion, respectively, indicating a graded suppression of sympathetic nervous activity. Plasma concentrations of arginine vasopressin were suppressed by 1.5 +/- 0.5 pg mL-1 (P < 0.05) during xiphoid immersion and by 2.0 +/- 0.5 pg mL-1 during neck immersion (P < 0.05 vs. xiphoid immersion). Forearm subcutaneous vascular resistance decreased to the same extent by 26 +/- 9 and 28 +/- 4% (P < 0.05), respectively, during both immersion procedures, whereas forearm skeletal muscle vascular resistance declined only during neck immersion by 27 +/- 6% (P < 0.05). In conclusion, graded central blood volume expansion initiated a graded decrease in sympathetic nervous activity and AVP-release. Changes in forearm subcutaneous vascular resistance, however, were not related to the gradual withdrawal of the sympathetic and neuroendocrine vasoconstrictor activity. Forearm skeletal muscle vasodilatation exhibited a more graded response with a detectable decrease only during immersion to the neck. Therefore, the forearm subcutaneous vasodilator response reaches saturation at a lower degree of central volume expansion than that of forearm skeletal muscle.

Adult↗

PubMed2005

Thermal effects of dorsal head immersion in cold water on nonshivering humans.

Personal floatation devices maintain either a semirecumbent flotation posture with the head and upper chest out of the water or a horizontal flotation posture with the dorsal head and whole body immersed. The contribution of dorsal head and upper chest immersion to core cooling in cold water was isolated when the confounding effect of shivering heat production was inhibited with meperidine (Demerol, 2.5 mg/kg). Six male volunteers were immersed four times for up to 60 min, or until esophageal temperature = 34 degrees C. An insulated hoodless dry suit or two different personal floatation devices were used to create four conditions: 1) body insulated, head out; 2) body insulated, dorsal head immersed; 3) body exposed, head (and upper chest) out; and 4) body exposed, dorsal head (and upper chest) immersed. When the body was insulated, dorsal head immersion did not affect core cooling rate (1.1 degrees C/h) compared with head-out conditions (0.7 degrees C/h). When the body was exposed, however, the rate of core cooling increased by 40% from 3.6 degrees C/h with the head out to 5.0 degrees C/h with the dorsal head and upper chest immersed (P < 0.01). Heat loss from the dorsal head and upper chest was approximately proportional to the extra surface area that was immersed (approximately 10%). The exaggerated core cooling during dorsal head immersion (40% increase) may result from the extra heat loss affecting a smaller thermal core due to intense thermal stimulation of the body and head and resultant peripheral vasoconstriction. Dorsal head and upper chest immersion in cold water increases the rate of core cooling and decreases potential survival time.

Adult↗

PubMed2005

Intranuclear cytoplasmic inclusions and nuclear grooves in fine needle aspiration smears of papillary thyroid carcinoma and its variants: advantage of the count under an oil-immersion objective over a high-power objective.

OBJECTIVE: To determine the advantage of examining fine needle aspiration (FNA) smears of papillary thyroid carcinoma (PTC) under a 100 x oil-immersion objective, which is capable of optically sectioning the cells. STUDY DESIGN: Two hundred neoplastic cells were counted under a high-power (40x) objective as well as oil-immersion (100x) objective in 54 PTC cases classified into variants: 14 follicular neoplasms, 8 Hürthle cell neoplasms, 5 medullary thyroid carcinomas and 9 hyperplastic lesions. The counts of cells with 2 important diagnostic features of PTC, intranuclear cytoplasmic inclusions (INCIs) and grooved nuclei, were compared between various groups and between high-power and oil-immersion objectives in each group. RESULTS: Cytomorphologic features, such as INCI and nuclear grooves, were visible usually under 2 or 3 focal planes under the oil-immersion objective as opposed to a single plane under the high-power objective. In PTC cases, the mean cell count, 10.1 (+/- 1.75 SE) with INCIs, under the oil-immersion objective was significantly higher than the count, 6.1 (+/- 1.32 SE), under the high-power objective (p = 0.023). INCIs were not observed under the high-power objectives in 11 (20.4%) PTC cases, but in 5 (45.5%) of these they were visible under the oil-immersion objective. In PTC the mean cell count, 88.0 (+/- 4.96 SE), with grooved nuclei under the oil-immersion objective was also significantly higher than the count, 69.5 (+/- 4.87 SE), under the high-power objective (p = 0.010). Under the high-power objective, < 20.0% of cells with grooved nuclei were observed in 12 (22.2%) cases of PTC. However, examination under the oil-immersion objective revealed > or = 20.0% cells with grooved nuclei in 9 (75%) of these. In PTC the mean cell counts with INCIs as well as grooved nuclei under the oil-immersion objective were significantly higher than those of follicular neoplasms, Hürthle cell neoplasms, medullary carcinoma and hyperplastic lesions. CONCLUSION: In PTC, examination of FNA smears for INCIs and grooved nuclei under an oil-immersion objective was diagnostically more useful as compared to a high-power objective.

Adult↗

PubMed1996

Maximal breath-holding time and immediate tissue CO2 storage capacity during head-out immersion in humans.

This study tested three possible mechanisms that could explain the prolonged breath-holds (BH) previously observed in humans during submersion in 35 degrees C (thermoneutral) water, including a reduced metabolism, a decreased CO2 sensitivity, and an increased CO2 storage capacity. During immersed BH (n = 13), maximal BH time was prolonged by 20.3% (P < 0.05), the rate of rise of end tidal partial pressure of carbon dioxide (PETCO2) was slower (P < 0.05) by 31% (compatible with increased CO2 storage capacity), but the breaking-point PETCO2 (CO2 sensitivity) and the rate of decrease of end tidal partial pressure of oxygen (metabolism) were unchanged. During air breathing (n = 5), immersion resulted in a significant decrease in tidal volume (11%), but did not affect O2 uptake, CO2 elimination (VCO2), or respiratory exchange ratio (R). During a 4-min CO2-rebreathing (n = 9), the slope of the hypercapnic ventilatory response curve (CO2 sensitivity index) was unchanged by immersion, but the significantly decreased VCO2, R, and rate of rise in PETCO2 during immersed rebreathing indicated an increase in the acute CO2 storage capacity (SC). The estimated SC (n = 9), based on an assumed cellular respiratory quotient of 0.8, were 0.52 (SEM 0.03) ml.kg-1.mmHg-1 for control and 0.66 (SEM 0.04) ml.kg-1.mmHg-1 for immersion. A proposed mechanism for the increased SC during immersed BH and during immersed rebreathing is that immersion accelerated CO2 redistribution in the body by increasing perfusion to some low-perfused, low-metabolism, and high-capacity tissues, such as resting skeletal muscle. The increased SC during immersion, however, did not correlate with the prolonged BH duration (n = 9, P > 0.05). The mechanism of the latter remains unclear.

Adult↗

PubMed2000

Human physiological responses to immersion into water of different temperatures.

To differentiate between the effect of cold and hydrostatic pressure on hormone and cardiovascular functions of man, a group of young men was examined during 1-h head-out immersions in water of different temperatures (32 degrees C, 20 degrees C and 14 degrees C). Immersion in water at 32 degrees C did not change rectal temperature and metabolic rate, but lowered heart rate (by 15%) and systolic and diastolic blood pressures (by 11 %, or 12%, respectively), compared to controls at ambient air temperature. Plasma renin activity, plasma cortisol and aldosterone concentrations were also lowered (by 46%, 34%, and 17%, respectively), while diuresis was increased by 107%. Immersion at 20 degrees C induced a similar decrease in plasma renin activity, heart rate and systolic and diastolic blood pressures as immersion at thermoneutrality, in spite of lowered rectal temperature and an increased metabolic rate by 93%. Plasma cortisol concentrations tended to decrease, while plasma aldosterone concentration was unchanged. Diuresis was increased by 89%. No significant differences in changes in diuresis, plasma renin activity and aldosterone concentration compared to subjects immersed to 32 degrees C were observed. Cold water immersion (14 degrees C) lowered rectal temperature and increased metabolic rate (by 350%), heart rate and systolic and diastolic blood pressure (by 5%, 7%, and 8%, respectively). Plasma noradrenaline and dopamine concentrations were increased by 530% and by 250% respectively, while diuresis increased by 163% (more than at 32 degrees C). Plasma aldosterone concentrations increased by 23%. Plasma renin activity was reduced as during immersion in water at the highest temperature. Cortisol concentrations tended to decrease. Plasma adrenaline concentrations remained unchanged. Changes in plasma renin activity were not related to changes in aldosterone concentrations. Immersion in water of different temperatures did not increase blood concentrations of cortisol. There was no correlation between changes in rectal temperature and changes in hormone production. Our data supported the hypothesis that physiological changes induced by water immersion are mediated by humoral control mechanisms, while responses induced by cold are mainly due to increased activity of the sympathetic nervous system.

Adult↗

PubMed1986

Dopamine blockade and natriuresis during water immersion in normal man.

Natriuresis was studied during water immersion in eight normal subjects either in the absence or in the presence of dopamine blockade by domperidone. Creatinine clearance showed no significant changes; urine flow remained significantly above control values during water immersion, implying persistent suppression of antidiuretic hormone. The marked natriuresis seen during water immersion alone was significantly blunted (P less than 0.05) but not abolished during water immersion plus domperidone. Suppression of the renin-aldosterone system by water immersion alone was not significantly different from that obtained during water immersion plus dopamine blockade. On the contrary, plasma prolactin levels, previously suppressed during water immersion alone, were significantly stimulated during water immersion plus domperidone, thus indirectly suggesting a role of dopamine in mediating the blunted natriuresis seen during water immersion.

Adult↗

PubMed2004

Effects of immersion water temperature on whole-body fluid distribution in humans.

AIM: In this study, we quantified acute changes in the intracellular and extracellular fluid compartments during upright neutral- and cold-water immersion. We hypothesized that, during short-term cold immersion, fluid shifts would be wholly restricted to the extracellular space. METHODS: Seven males were immersed 30 days apart: control (33.3 degrees SD 0.6 degrees C); and cold (18.1 degrees SD 0.3 degrees C). Posture was controlled for 4 h prior to a 60-min seated immersion. RESULTS: Significant reductions in terminal oesophageal (36.9 degrees +/- 0.1 degrees -36.3 degrees +/- 0.1 degrees C) and mean skin temperatures (30.3 degrees +/- 0.3 degrees -23.0 degrees +/- 0.3 degrees C) were observed during the cold, but not the control immersion. Both immersions elicited a reduction in intracellular fluid [20.17 +/- 6.02 mL kg(-1) (control) vs. 22.72 +/- 9.90 mL kg(-1)], while total body water (TBW) remained stable. However, significant plasma volume (PV) divergence was apparent between the trials at 60 min [12.5 +/- 1.0% (control) vs. 6.1 +/- 3.1%; P < 0.05], along with a significant haemodilution in the control state (P < 0.05). Plasma atrial natriuretic peptide concentration increased from 18.0 +/- 1.6 to 58.7 +/- 15.1 ng L(-1) (P < 0.05) during cold immersion, consistent with its role in PV regulation. We observed that, regardless of the direction of the PV change, both upright immersions elicited reductions in intracellular fluid. CONCLUSION: These observations have two implications. First, one cannot assume that PV changes reflect those of the entire extracellular compartment. Second, since immersion also increases interstitial fluid pressure, fluid leaving the interstitium must have been rapidly replaced by intracellular water.

Adult↗

PubMed1988

Limitations of facial immersion as a test of parasympathetic activity in man.

1. The heart rate response to immersion of the face in water, as an isolated manoeuvre or in combination with apnoea, was studied in eight normal volunteers to establish the conditions under which it could be used as a standardized, simple, non-invasive and reproducible test of parasympathetic activity. 2. The following procedures were evaluated: (a) 10 s apnoea in air at different lung volumes; (b) facial immersion in water for 2 min at various temperatures (5, 15 and 25 degrees C), with respiration maintained through a closed circuit; (c) combination of immersion and apnoea at different lung volumes. Three volunteers were re-evaluated after pharmacological blockade with atropine sulphate (0.04 mg/kg body weight). 3. The results showed that: (a) apnoea in air triggered lung volume-dependent heart rate responses; (b) facial immersion in water induced transient bradycardia which was maximum between 20 and 30 s of immersion; (c) there was no appreciable difference in the bradycardia evoked by immersion at different temperatures; (d) the combination of immersion and apnoea caused heterogeneous heart rate responses with no potentiation of bradycardia in relation to each manoeuvre as performed separately; (e) atropine did not reduce the magnitude of bradycardia induced by immersion in two of the subjects studied. 4. The variability of responses observed in the present study was probably due to the multiple receptors and afferent pathways that are simultaneously excited during these manoeuvres. As a consequence, the autonomic efferent response will depend on the unpredictable net effect of interaction of these mechanisms. This is a limiting factor for the standardization of this test as a simple and reproducible method for the assessment of parasympathetic activity. 5. Furthermore, the results obtained under pharmacological blockade indicate that the vagal efferent mechanism is not the only factor responsible for the bradycardia caused by facial immersion without apnoea.

Adult↗

PubMed1995

Role of hemodilution on renal responses to water immersion in humans.

The present experiments were designed to elucidate 1) the role of the lower extremity capillary bed in decreasing plasma colloid osmotic pressure (COP) during immersion of humans (n = 8) for 6 h, and 2) the extent to which the natriuresis of water immersion is triggered by this decrease in COP. Irrespective of the depth, COPs were very similar during the immersion procedures, varying between 25.3 +/- 0.5 and 26.4 +/- 0.6 mmHg, which was significantly lower than during control (28.3 +/- 0.3 and 28.6 +/- 0.3 mmHg). During neck immersion, central venous pressure rose instantly by approximately 12 mmHg (P < 0.05) and remained elevated. Only a transient, marginal increase (1.6 +/- 0.7 mmHg) occurred during hip immersion. Cumulated sodium excretion during seated control, hip immersion, and neck immersion, respectively, differed significantly (30 +/- 5, 45 +/- 5, and 101 +/- 6 mmol). It is concluded that the decrease in COP during immersion is primarily due to fluid shifts occurring in the capillary bed of the legs and that this may account for up to 25% of the immersion-induced increase in renal sodium excretion.

Adult↗

PubMed1977

Immersion diuresis in dogs.

The mechanism of diuresis during the 1st h of immersion was investigated using anesthetized dogs. Four different experiments were carried out. First, left atrial transmural pressure was measured before, during, and after immersion. The data suggest that, although the left atrium may or may not be stretched depending on the conditions of immersion, the amount of diuresis is independent of the amount of left atrial stretch, and therefore a causal relationship between diuresis and left atrial stretch could not be established. Second, bilateral cervical vagotomy was carried out. Immersion diuresis sometimes occurred despite this vagotomy, suggesting that the left atrial stretch reflex was not participating in those cases. Third, negative-pressure breathing was carried out to simulate the negative transthoracic pressure associated with uncompensated immersion. The average left atrial transmural pressure did not change. A slight hemodilution and a moderate diuresis occurred. There was no correlation between changes in left atrial transmural pressure and changes in urine ouput. Fourth, blood studies were done on splenectomized dogs subjected to immersion. Hemodilution occurred and was most marked in dogs which had had their kidneys removed. The hemodilution is sufficient to explain the early phase of the immersion diuresis. The data suggest that, in anesthetized dogs, hemodilution is the probable initiator of diuresis upon immersion and that, in dogs, left atrial stretch is unrelated to diuresis during immersion or negative-pressure breathing.

Animals↗

PubMed1986

Effect of hydration on plasma volume and endocrine responses to water immersion.

To determine the effect of hydration on the early osmotic and intravascular volume and endocrine responses to water immersion the hematocrit, hemoglobin, plasma renin activity (PRA), and plasma electrolyte, aldosterone (PA), and vasopressin (PVP) concentrations were measured during immersion following 24-h dehydration; these were compared with corresponding values following rapid rehydration. Six men and one woman (age 23-46 yr) underwent 45 min of standing immersion to the neck preceded by 45-min standing without immersion, first dehydrated, and then 105 min later after rehydration with water. Immersion caused an isotonic expansion of the plasma volume (P less than 0.001), which occurred independently of hydration status. Suppression of PRA (P less than 0.001) and PA (P less than 0.001) during both immersions also occurred independently of hydration status. Suppression of plasma vasopressin was observed during dehydrated immersion (P less than 0.001) but not during rehydrated immersion. It is concluded that plasma tonicity is not a factor influencing PVP suppression during water immersion.

Adult↗

PubMed1989

Prolonged whole-body cold water immersion: fluid and ion shifts.

To characterize fluid and ion shifts during prolonged whole-body immersion, 16 divers wearing dry suits completed four whole-body immersions in 5 degrees C water during each of two 5-day air saturation dives at 6.1 msw. One immersion was conducted at 1000 (AM) and one at 2200 (PM) so that diurnal variations could be evaluated. Fifty-four hours separated the immersions, which lasted up to 6 h; 9 days separated each air saturation dive. Blood was collected before and after immersion; urine was collected for 12 h before, during, and after immersion for a total of 24 h. Plasma volume decreased significantly and to the same extent (approximately 17%) during both AM and PM immersions. Urine flow increased by 236.1 +/- 38.7 and 296.3 +/- 52.0%, urinary excretion of Na increased by 290.4 +/- 89.0 and 329.5 +/- 77.0%, K by 245.0 +/- 73.4 and 215.5 +/- 44.6%, Ca by 211.0 +/- 31.4 and 241.1 +/- 50.4%, Mg by 201.4 +/- 45.9 and 165.3 +/- 287%, and Zn by 427.8 +/- 93.7 and 301.9 +/- 75.4% during AM and PM immersions, respectively, compared with preimmersion. Urine flow and K excretion were significantly higher during the AM than PM. In summary, when subjects are immersed in cold water for prolonged periods, combined with a slow rate of body cooling afforded by thermal protection and enforced intermittent exercise, there is diuresis, decreased plasma volume, and increased excretions of Na, K, Ca, Mg, and Zn.

Adult↗

PubMed1990

[Development of an improved system for monitoring the peripheral circulation and its application. Part 2. Its application to the cold water immersion test in workers using vibratory tools].

Using an improved system for measuring skin blood flow by the thermal clearance curve, the change of the skin blood flow in the finger (finger blood flow) of the workers using vibratory tools induced by 10 degrees C cold water immersion for 10 min was observed in order to clarify the pathogenesis of vibration-induced white finger (VWF) from the aspect of peripheral circulatory function and simultaneously to demonstrate the efficiency of the system. The subjects constituted a group of 10 workers with VWF (VWF group) and 10 healthy workers without a history of hand-arm symptoms (control group). Ages and years of exposure to vibration in the two group were almost equal. The results were as follows. 1) While the finger blood flow in the control group was remarkably decreased at 1 min after the immersion, the decrease in the VWF group was low as compared with that in the control group. This result shows that vasoconstriction just after the immersion in VWF patients is not as great as that in the control group. 2) The finger blood flow in the control group at 5 min after the immersion was increased. In contrast no increase in the VWF group was observed. These results showed that cold-induced vasodilatation (CIVD) in VWF patients diminished. 3) An increase of the finger blood flow at 1 min after stopping the immersion was observed in the VWF group. These results suggest that the property of reaction to cold in VWF patients is not excessive vasoconstriction as has been hypothesized, but the diminution of CIVD. Apart from 10 workers of VWF group, observing the change of the finger blood flow in a case in which VWF was provoked by the immersion, the author found an abnormal decrease of the finger blood flow at 5 min after the immersion. This finding supports the hypothesis that the diminution of CIVD plays an important role in VWF attack as well. Concerning the characteristics of peripheral circulatory function in VWF patients, it can therefore be considered that its reaction in VWF attack is vasospasms, while the reaction to cold is the diminution of CIVD in the non-attack phase. The cold water immersion test using the system was recognized to be useful for diagnostic examination because the estimation of finger blood flows at both measuring points, 1 min and 5 min after the immersion, could fairly well discriminate VWF patients from healthy workers.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗

PubMed1999

Cardiovascular regulation during water immersion.

Head-out water immersion at thermoneutral temperature (34-35 degrees C) increases cardiac output for a given O2 consumption, leading to a relative hyperperfusion of peripheral tissues. To determine if subjects immersed in water at a colder temperature show similar responses and to explore the significance of the hyperperfusion, cardiovascular functions were investigated (impedance cardiography) on 10 men at rest and while performing exercise on a leg cycle ergometer (delta M = approximately 95 W.m-2) in air and in water at 34.5 degrees C and 30 degrees C, respectively. In subjects resting in water, the cardiac output increased by approximately 50% compared to that in air, mainly due to a rise in stroke volume. The stroke volume change tended to be greater in 30 degrees C water than in 34.5 degrees C water, and this was due to a greater increase in cardiac preload, as indicated by a significantly greater left ventricular end-diastolic volume. Arterial systolic pressure rose slightly during water immersion. Arterial diastolic pressure remained unchanged in 34.5 degrees C water, but it rose in 30 degrees C water. The total peripheral resistance fell 37% in 34.5 degrees C water and 32% in 30 degrees C water. Both in air and in water, mild exercise increased the cardiac output, and this was mainly due to an increase in heart rate. Since, however, the stroke volume increased with water immersion, cardiac output at a given work load appeared to be significantly higher in water than in air. The arterial pressures did not decrease with water immersion, despite a marked reduction in total peripheral resistance. These results suggest that 1) during cold water immersion, peripheral vasoconstriction provides an additional increase in cardiac preload, leading to a further increase in the stroke volume compared to that of the thermoneutral water immersion, 2) the mechanism of cardiovascular adjustment during dynamic exercise is not changed by the persistent increase in cardiac preload in water immersion, and 3) a relatively high cardiac output during water immersion is to maintain a proper arterial pressure in the face of reduced vascular resistance.

Adult↗